Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GI Physiology > 43 Digestion and Absorption > Flashcards

43 Digestion and Absorption Flashcards

1
Q

Name 3 structural modifications for Intestinal Digestion & Absorption

A
  1. Folding of intestinal surface
  2. Presence of villi
  3. Presence of microvilli
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the functions of villus cells? What is the disease if there is loss of villi?

A

Digestion, Absorption, Secretion;

Celiac disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the 2 functions of crypt cells?

A
  1. Undergo mitosis to replace worn out villus cells (high turnover rate)
  2. Active secretion
    (over-secretion via CFTR channels might cause secretory diarrhea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are luminal enzymes and membrane-bound enzymes?

A

Luminal enzymes are from salivary glands, stomach and pancreas.

Membrane-bound enzymes are hydrolytic enzymes inserted in brush border.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which of the followings is/are not membrane-bound enzyme?

  1. Enterokinase
  2. Amylase
  3. Pepsin
  4. Disaccharidases
  5. Phospholipase A2
  6. Peptidases
A

Amylase
Pepsin
Phospholipase A2
are all luminal enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is auto-digestion in pancreas prevented?

Hint: Trypsinogen > Tyrpsin

A 
Duodenal bound (membrane-bound) enzyme enterokinase cleaves trypsinogen to trypsin.
All precursors (trypsinogen) are inactive in the pancreas.

Trypsin is autocatalytic and will undergo positive feedback, causes the rest trypsinogen to be mature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the disease arises from the premature of trypsinogen in the pancreas causing auto digestion in the acinar cells ?

A

Acute pancreatitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is auto-digestion prevented by the chief cells?

A

Chief cells secrete pepsinogen in stomach wall into the gastric lumen, which becomes fully active form in the mucosal surface & begins initial protein digestion.

Pepsinogen exposes its active site only when under pH stimulation
Also autocatalytic and causes the rest of the pepsinogen to become pepsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

List all examples of Monosaccharides, Oligosaccharides and Polysaccharides

A

Monosaccharides: glucose, galactose, fructose

Oligosaccharides: maltose ,lactose, sucrose

Polysaccharides: Glycogen, starch, cellulose*

*cellulose: indigestible due to the presence of beta1-4 peptide bond, BUT acts as dietary fibre or roughage that stimulates intestinal motility and thus prevents constipation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is glucose absorbed?

A 
By secondary active transport which is Na+ dependent;
Requires SGLT1 (Sodium dependent glucose transporter)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is galactose absorbed?

A 
By secondary active transport which is Na+ dependent;
Requires SGLT1 (Sodium dependent glucose transporter)

Same as glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is fructose absorbed?

A

Facilitated diffusion;
Separate transport: GLUT5

Therefore, SGLT 1 defect causes glucose and galactose malabsorption, but normal fructose absorption is assured as the transport mechanism is different.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Alpha-amylases can cut:
A. a-1,4 glycosidic linkage
B. a-1,6-linkage
C. Both linkages

A

A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the differences between amylose and amylopectin?

A 
In terms of branching, 
Amylose: unbranched (straight) chain of D-glucose
(only contains a-1,4-linkage) 
Amylase: highly branched 
(with a-1,4 and a-1,6-linkages)

In terms of enzymes needed for degradation,
Amylose requires a-amylase;
Amylase requires membrane bound enzymes: a-dextrin

a-dextrin includes:

  1. A-dextrinase break a-1,6-linkages
  2. Glucoamylase break a-1,4-linkages
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which kind of Na+ dependent carrier transporter is predominantly expressed in SI?

A

SGLT 1

Glucose and galactose: competitive absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which of the following statements are true:
A. Glucose absorption facilitates Na + transport
B. Na+ transport facilitates glucose absorption

A

Both A and B, by creating a concentration gradient

17
Q

Which transporter created the Na+ gradient?

A

Na+/K+ ATPase

by pumping 3Na+ out and 2K+ in

18
Q 
After glucose and galactose entered the enterocyte, it enters the blood via \_\_\_\_\_\_ by \_\_\_\_\_\_\_\_.
A. GLUT5; facilitated diffusion
B. GLUT 2; facilitated diffusion
C. GLUT 5; active transport
D. GLUT 2; active transport
A

B

19
Q

What does oral rehydration therapy contain? What is it for? How does it achieve this goal?

A

Glucose containing saline solution,
1 glucose/AA > Na+ and Cl- > 3 osmotically active molecules

For secretory/ watery diarrhea

Because glucose facilitates Na+ absorption, no more diarrhea

20
Q

Partial complete digestion is achieved by ______ enzyme while complete digestion is achieved by ________ enzyme.
Why can the above enzyme achieve complete digestion?

A

Luminal enzyme (esp secreted by the pancreas);

Membrane-bound enzyme

Overlapping specificity.
(e.g. sucrase 25% specificity to digest maltose, 100 % specificity to digest sucrose)

Lactase is 100% specific to lactose, thus lactase deficiency will lead to malabsorption of lactose, causing lactose intolerance > diarrhea

21
Q

What isoform of amino acid is absorbable by humans?

A

L-isoform

22
Q

What type of amino acid do Phe, Tyr, Glr belong to?

A

Neutral

23
Q

Basic: Lys, Arg (with additional NH3+)
Acidic: Glu, Asp (with additional COO-)
Other than neutral, what is the last type of aa?
List 2 examples of amino acid of this group.

A

Imino;
Proline, beta and y amino acids
e.g. GABA

24
Q

What are the 2 sources of protein for digestion?

A
  1. Dietary (Exogenous) protein

2. Enzymes and mucus (Endogenous) from GI secretion

25
Q

What are the 2 types of peptidases? What are they?

A

Endopeptidases

  • luminal enzymes from stomach and pancreas
  • Hydrolyses interior peptide bonds

Exopeptidases

  • Carboxypeptidases from pancreas
  • Aminopeptidases from membrane bound enterocytes
  • Hydrolyses external peptide bonds
26
Q

What are the 3 absorbable forms of proteins? What transporter is used respectively?

A

Free amino acids:
Na+ dependent amino acid transporter (40%)

Dipeptides:
Na+ dependent peptide transporter

Tripeptides:
Na+ dependent peptide transporter

Di+ Tri: 60%

27
Q

How are proteins absorbed in newborns?

A

By pinocytosis, immunologically significant

28
Q

What are the 4 categories of free amino acid carrier?

A
  1. Neutral (NBB, Neutral brush border)
  2. Basic (Cationic NH+)
  3. Acidic (Anionic COO-)
  4. Imino
  5. Neutral (NBB, Neutral brush border):
    Aromatic (Phe, Tyr, Trp)
    Aliphatic (Ala, Gly, Leu, Ile, Val, Ser, Thr, Cys, Met)
  6. Basic (Cationic NH+):
    Lys, Arg
  7. Acidic (Anionic COO-):
    Glu, Asp
  8. Imino:
    pro
29
Q

60%: Small peptides entering the _______ membrane via Na+ dependent peptide transporters.
40%: Free amino acids entering the ________ membrane via Na+ dependent amino acid transporters.
In the _________, only simple amino acids can be absorbed, and thus oligopeptides must become amino acids to be absorbed.

A

Brush-border membrane/ Apical membrane;

Brush-border membrane/ Apical membrane;

Basolateral membrane (BLM)

30
Q

3 genetic orders of amino acid transport due to defects in BBM or BLM.

A
  1. Hartnup’s disease
  2. Cystinuria
  3. Lysinuric protein intolerance
31
Q

What causes Hartnup’s disease? How it can be treated?

A

The lack of free tryptophan.
Still can be absorbed as oligopeptides and transformed to free tryptophan as an aid, but still insufficient.

Treatment: more proteins intake/ more free tryptophan intake

32
Q

What causes Cystinuria? How it can be treated?

A

The defect in amino acid transporters and (cysteine transporters).

Cysteine can still be absorbed in the form of oligopeptides as an aid

Treatment: more proteins intake/ more free cysteine intake

33
Q

What causes Lysinuric protein intolerance? How it can be treated?

A

The defect in amino acid transporter (lysine transporters).

Can only be treated with lysine infusion.

GI Physiology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions